Stable isotopes in tree rings as climate and stress indicators

Stable isotopes are an important tool in paleoclimatic research. Measurements on fumigated plants and on tree rings of naturally grown wood stands indicate the potential of carbon and oxygen isotopes as climate and stress indicators.

Carbon and oxygen isotope ratios on tree rings samples from the Central Swiss Plateau are well correlated with climate parameters. Carbon isotopes reflect mainly the amaunt of precipitation during the growing season, whereas oxygen isotopes register the isotopic composition of precipitation. The importance of site conditions is demonstrated: for dry sites the variations are significantly larger than for wet sites.

The correlations with climate parameters over the last few decades are used as calibration for past isotope variations in tree rings. To better understand the underlying processes, the isotope ratio changes are discussed on the basis of mechanistical isotope incorporation models.